Question: $\left(-10x + 10\right)\left(-x - 10\right) = \ ?$
Solution: $= -10x \cdot \left(-x - 10\right) + 10 \cdot \left(-x - 10\right)$ $= \left( -10x \cdot -x \right) + \left( -10x \cdot -10 \right) + \left( 10 \cdot -x \right) + \left( 10 \cdot -10 \right)$ $= 10x^2 + \left( -10x \cdot -10 \right) + \left( 10 \cdot -x \right) + \left( 10 \cdot -10 \right)$ $= 10x^2 + \left( 100x - 10x \right) + \left( 10 \cdot -10 \right)$ $= 10x^2 + 90x + \left( 10 \cdot -10 \right)$ $= 10x^2 + 90x - 100$